Deaths from opioid overdoses increased again in Minnesota last year, despite heightened law enforcement and a massive decline in doctors prescribing opioid painkillers.

A Star Tribune analysis of state death certificate data found 402 opioid-related deaths in 2016, up from 344 in 2015.

Overdoses of illicit heroin and potent synthetic opioids such as fentanyl drove the increase. There was little change in the number of deaths caused by common painkillers such as hydrocodone that have been blamed for starting the opioid epidemic.

The trend suggests that efforts to reduce painkiller prescriptions won’t be enough to reduce fatalities, because many who started abusing prescriptions have switched to heroin.

“It’s kind of like we let the cat out of the bag, and now there is a separate opioid epidemic that has sort of gained its own life, independent of pharmaceutical prescribing,” said Dr. Charlie Reznikoff, an addiction specialist at Hennepin County Medical Center. “And we need to address that separately.”

Last year was the first, since the opioid epidemic emerged in the late 1990s, in which heroin was implicated in more deaths (147) than common opioid painkillers (140), the Star Tribune’s analysis found.

Deaths related to synthetic opioids doubled from 50 in 2015 to 101 in 2016. That trend appears to be continuing, given last week’s announcement by the Hennepin County medical examiner of 11 deaths so far this year from a new synthetic known as carfentanil.

Used legally as a tranquilizer in large game animals, carfentanil is considerably more potent than other opioids. Like fentanyl, it also appears to be compounded into illicit doses of heroin because it is cheaper for drug dealers to make, transport and sell — making street drugs far more dangerous.

“Being a heroin addict has become significantly riskier,” said Dr. Mark Willenbring, a former federal drug research administrator who provides opioid treatment in St. Paul.

While Minnesota has one of the lowest rates of opioid deaths in the U.S., state health officials have responded by increasing access to the so-called rescue drug naloxone for emergency treatment of overdoses. The state also sought to decrease opioid prescriptions by using electronic monitoring to identify doctors who overprescribe opioids and addicts who shop for them among providers.

Reports of misuse of oxycodone and hydrocodone to the Minneapolis Poison Control Center consequently declined from 2015 to 2016. Hydrocodone remains the most commonly prescribed drug in Minnesota, but only 87,962 prescriptions were dispensed last December compared with 113,656 in December 2014, according to the April Drug Abuse Trends report by addiction expert Carol Falkowski.

Health officials said they were disappointed that these efforts didn’t reduce the number of deaths, but not surprised because of the amount of fentanyl in the illicit market.

“Its potency is fatal,” Falkowski said. “So even with a static number of opioid users, deaths would rise.”

Advocates such as Dr. Chris Johnson, who leads a task force revising Minnesota’s opioid-prescribing guidelines, have traced the epidemic back to marketing of painkillers such as hydrocodone and oxycodone and introduction of the 10-point pain scale that made pain a vital sign for treatment.

Death certificates referencing those two painkillers by name barely increased from 82 in 2015 to 84 last year. An additional 70 deaths last year were linked to methadone, an opioid replacement that treats addictions but can be abused.

Death certificates analyzed

The Star Tribune analysis was based on death certificate data obtained through an open records request to the Minnesota Department of Health, which later this year will release its own report on opioid deaths in 2016.

One possibility for the increase in deaths is that restrictions on prescription opioids drove addicts to heroin, which is increasingly dangerous because it is being mixed surreptitiously with fentanyl, Reznikoff said. “The margin for error is so small that, as soon as you start messing around with [fentanyl], you get in trouble really quickly.”

Relatives of Nick Petrick doubt the 29-year-old from New Prague knew he took fentanyl when he died from an overdose. His death certificate in 2016 was one of 38 to list heroin and fentanyl as causes.

Petrick started using heroin four years earlier, and suffered relapses despite treatment and hopes for a future with a girlfriend and construction work, his mother said. But after leaving for work April 11, 2016, Petrick went missing and was found dead four days later holding a lighter and a hollowed-out pen in his car in an Eden Prairie parking lot.

“I really doubt he knew what he was getting,” said his mother, Julie Petrick. “I had never even heard of fentanyl until his autopsy.”

Six days after that, authorities found Prince dead in his Chanhassen home of a fentanyl overdose. Search warrant records indicate that fentanyl pills in his home were mislabeled as hydrocodone — raising the possibility that he, too, didn’t know what he was taking.

‘Self-sustaining’ epidemic

Overdose victims are getting younger as the types of opioids involved are shifting. The average age of an opioid-related fatality dropped from 42 in 2015 to 39 last year.

Willenbring said fear of deaths and synthetic drugs might hasten the end of the epidemic. Deaths in 2016 likely involved addicts who started using opioids years ago, he said. But surveys show declines in teenagers trying opioids, so deaths should decline.

“They observe what happens to their older siblings and older siblings’ friends,” he said, “and they see them dying of heroin overdoses and think, ‘Oh, that crap is really dangerous. I’m not going to start that.’ ”

Even if new users decline, the 5 million existing addicts means the U.S. will be dealing with the epidemic for years, Reznikoff said. Deaths often occur in people who relapse after treatment and take doses they can no longer tolerate.

“If you have 5 million opioid addicts and only a fraction of them are appropriately treated, they will perpetuate the opioid epidemic themselves,” he said. “It’ll be self-sustaining. They don’t need doctors giving them pharmaceuticals anymore.”

While doctors have prescribed fewer opioids, Reznikoff said they need to go further by providing addiction medications. Only 170 doctors in the state are listed by the U.S. Substance Abuse and Mental Health Services Administration as trained to prescribe Suboxone, a drug that mimics opioids and eliminates cravings.

“It’s harder to get doctors to buy into the second prong, the dealing with addicts prong,” Reznikoff said.

Petrick said her son got Suboxone on the street, because local doctors either didn’t provide it or were already at their federal threshold for Suboxone patients. She remains angry that dealers would make their drugs even more lethal.

Beverly Burrell, the dealer who allegedly provided the fatal dose to Petrick, was found guilty last week of third-degree murder in the heroin overdose of Luke Ronnei, 20, of Chanhassen. She has been charged in Petrick’s death as well.

“So many deaths, it’s crazy,” Julie Petrick said. “They have to go after the dealers.”

Jeremy Olson is a Pulitzer Prize-winning reporter covering health care for the Star Tribune. Trained in investigative and computer-assisted reporting, Olson has covered politics, social services, and family issues.

Democratic Gov. Tim Walz is the first Minnesota governor to publicly indicate support for legalizing recreational marijuana, giving activists fresh hope the state might pass the measure this year. But Minnesota opponents are lining up against legalization.